Processing parameters adopted
during HPDC were listed in Table 1. To meet the requirement of
the SEM observations, i.e. the observation range was 72.5 mm,
samples for in situ tensile test and metallographic observation
were retrieved at locations A (without defect band) and B (with
defect band) in plate sample with T of 5 mm, as shown in Fig. 1a.
The in situ tensile test was carried out in a SEM chamber at a
deformation speed of 0.001 mm/s under ambient temperature
(20 °C). All of the metallographic samples were etched with a diluted
acetic acid solution, which comprised 50 ml distilled water,
150 ml anhydrous ethyl alcohol and 1 ml glacial acetic acid. The
fracture surface and microstructure was observed with a SEM